Under certain road conditions, such as on undivided two-way roads, a flagman uses a STOP/SLOW sign (paddle) to control traffic.
One side of the paddle displays a “STOP” message, and the other side of the paddle displays a “SLOW” message. When controlled traffic is shown the “STOP” side of the paddle, opposing traffic is shown the “SLOW” side of the paddle. This is, in most cases, not only acceptable, but also desirable. In some cases, a flagman wants to control traffic in one direction only. The flagman faces oncoming traffic and displays the paddle, regulating oncoming traffic without intending to regulate traffic traveling in the opposite direction (opposing traffic). However, opposing traffic can be unintentionally regulated because the STOP/SLOW paddle is in full view from both directions. When controlled traffic is shown the “SLOW” side of the paddle, an unintentional and potentially dangerous consequence is that opposing traffic is shown the “STOP” side of the paddle. While the flagman does not intend to convey a “STOP” message to opposing traffic, the message is conveyed. A motorist may see the “STOP” sign and stop, creating the potential for rear-end collisions and chain reaction pile-ups.
An illustration is the Texas Department of Transportation (TXDOT) Traffic Control Plan (TCP) TTP TCP-2-04 for 2 Lane, Undivided with Shoulders scenarios. While performing motorist surveys using this TCP, vehicles must be brought to a full stop to allow surveys to take place. When oncoming vehicles are shown the “SLOW” sign, opposing traffic can clearly see the backside of the STOP/SLOW paddle displaying a “STOP” sign.
The Manual on Uniform Traffic Control Devices (MUTCD) is the Federal Highway Administration's guide to traffic signs, barriers, construction zone traffic control plans, and similar items. The specifications for STOP/SLOW paddles are in Chapter 6, Section 6E. These specifications can be found at the following URL:
http://mutcd.fhwa.dot.gov/HTM/2003/part6/part6e.htm
These federal government specifications provide guidance for flaggers, including apparel, signaling devices like STOP/SLOW paddles, flagger procedures, and flagger stations. However, the MUTCD does not address the issue of motorists unintentionally being shown a “STOP” message.
Therefore, there is a need for a signaling device which allows a flagman to effectively control the messages displayed to both directions of traffic.